1. Field of the Invention
The present invention relates to a recording and reproducing (hereinafter called “recording reproduction”) apparatus that records and reproduces data on and from a multilayer recordable recording medium.
2. Description of the Related Art
Multilayer recordable recording mediums have recently been put forward in order to enhance recording capacity.
A recording reproduction apparatus that subjects a recording medium to multilayer recording is configured as follows.
Specifically, a related-art recording reproduction apparatus is made up of a rotary drive unit that rotationally drives a multilayer recordable recording medium; a lens disposed opposite the recording medium rotationally driven by the rotary drive unit; and a recording reproduction light source for feeding recording reproduction light to the lens; and an address light source for feeding address light to the lens. Patent Document 1 provided below is available as a document including descriptions about a technique relevant to a related-art recording reproduction apparatus.    Patent Document 1: JP-A-2002-150567
In the related-art recording reproduction apparatus, reproduction of a multilayer record does not become stable.
Namely, in order to record information in multiple layers in a recording medium, the lens is made up of a reference-light-side recording reproduction lens and a recording-light-side recording reproduction lens, which are opposed each other with a recording medium interposed therebetween. During recording, recording operation is performed by emitting a reference light beam from the reference-light-side recording reproduction lens to the inside of a recording medium and emitting a recording light beam from the recording-light-side recording reproduction lens to the inside of the recording medium, to thus generate interference fringes at a point of intersection between the light beams.
Next, during reproduction, recorded data are reproduced by emitting the reference light beam toward an object recording layer by way of the reference-light-side recording reproduction lens, to thus reflect the light by unit of interference fringes of the recording layer, and feeding the reflected light beam to a light receiving element by way of the reference-light-side recording reproduction lens.
Provided that the object recording layer is an interior layer; for instance, the 50th interior layer, 1st to 49th interference fringes are present in front of the objective recording layer. Therefore, during reproduction, light beams reflected from the 1st to 49th interference fringes located in front of the object recording layer are mixed as noise into a light beam reflected from the 50th layer, as a result of which reproduction of the multilayer record often becomes unstable.